The present invention relates to an apparatus for preventing clouding of a semiconductor wafer. More particularly, the invention is concerned with an apparatus which maintains at least the sulfur oxides concentration out of the sulfur oxides concentration and the nitrogen oxides concentration in the atmosphere of a semiconductor wafer treating zone below a predetermined level, so as to prevent clouding of a mirror-finished semiconductor wafer surface.
It is known that a mirror-finished semiconductor wafer surface treated in a wafer treating zone is gradually clouded by precipitates of components contained in the treating atmosphere such as water, nitrogen oxides (NOx), sulfur oxides (SOx), ammonia and so forth. Such clouding of the mirror-finished wafer surface seriously impedes subsequent steps of the semiconductor production process.
An apparatus have been proposed in order to eliminate the problem of clouding. For instance, an apparatus has been proposed in which the air in the semiconductor wafer treating zone is treated with a water absorbent or a dehumidifier so as to remove moisture content in the region near the semiconductor wafer surface. An apparatus also has been proposed in which the amount of alkali component derived from a semiconductor wafer scrubbing chamber is minimized.
Unfortunately, however, these known apparatus suffer from the following problems.
Namely, since the treatment of a semiconductor wafer essentially requires that the treating atmosphere contains an adequate amount of water so that the apparatus of the first-mentioned type is materially not allowed to reduce the water or moisture content to a level which is low enough to prevent clouding. The second-mentioned method also encounters with difficulty in reducing the alkali content to a level low enough to prevent clouding, because alkali substance such as ammonia is used in a large amount in a scrubbing chamber in which a scrubbing operation is conducted as a step immediately before the treatment of the wafer.
Therefore, it has been impossible to sufficiently prevent clouding of the semiconductor wafer with known techniques.